This is one of my all-time favorite movies, not only for the comedy but the hopeful nature of four kids saving the world during an alien invasion.
The only bad reviews I've seen are, in my opinion, ignorant adults that don't realize this movie's demographic is most likely teens. Between the childish feeling and the "mature" dialogue, I'd say it's safe to assume the main audience intended was somewhere between adults and children. "The dialogue feels like the perspective of a young person trying to make a statement in our society." Coming from a "young person", no one over the age of thirty lets anyone mildly younger than them make a statement, so I give the movie props for actually trying, talking about learning disabilities, financial issues, lack of parental guidance, etc.
Most of the negative reviews are about the "inappropriate" dialogue. "Mature jokes for young kids might have worked in a young adult-type film, but this was for a kid's camp?!" "There are minors talking about sexual intercourse with other minors." The second of which never happened, I've watched this movie countless times and I'd say there are, at max, two sex jokes. (Made by the ADULTS at the beginning of the movie, and aren't brought up again.)
The most in-touch adult talking about this film said, "I know parents hate the raunchy humor but our kids are hearing that via social media and the internet." Adults are so quick to disagree with inappropriate conversations, and then say even more vulgar things at the dinner table.
Overall the movie was incredible. Yes, while it could've been better, ALL movies can be picked apart and found flaws within. But you know, I'm just a young person trying to make a statement in our society.